China proposed a CO2 mitigation target in 2020 to deal with anthropogenic global climate change. Chinese policy makers mainly focus on three factors comprising consumption structure changes, energy technology development, and new energy increments. In addition, sectoral CO2 reduction is increasingly concerned in the world. Thus, it is significant to investigate integrated impacts of three factors to China's CO2 mitigation target as well as to identify key economic sectors for achieving this target. In this study, energy demand and CO2 emission in 2020 are predicted. Five scenarios are generated to illustrate the contributions of three factors. In addition, twelve key economic sectors for reducing energy demand and CO2 emission are identified from both production and final demand perspectives. Under integrated impacts of three factors, China's CO2 intensity per unit gross domestic product in 2020 will decrease by about 43.9% in 2020 than 2005 level. In the short term, China's CO2 mitigation will be highly dependent on energy technology development. In the long term, it will mainly rely on reshaped consumption structure changes and new energy development. In addition, China's future policies should focus on 12 identified key economic sectors.